Authenticity identification of animal species in characteristic milk by integration of shotgun proteomics and scheduled multiple reaction monitoring (MRM) based on tandem mass spectrometry

Milk is one of the oldest natural dairies with high value, which has different species including cow, camel, donkey, goat, sheep, buffalo, yak and et al. However, economically motivated adulteration of non-cow milk with cheaper cow milk occurs frequently. To develop a high-throughput approach for milk species authentication, integration of shotgun proteomics and scheduled multiple reaction monitoring (MRM) was developed. In total, 37 specific peptides were screened as unique to different species. Specific peptides processing stability was investigated under different treatment (heat, pressure, fermentation). Subsequently, four quantitative ion pairs of peptides from cow milk and six quantitative ion pairs of peptides from six non-cow milks were selected for the adulteration quantitative analysis. The method is capable of detection adulteration in the range of 1%-100%, and the quantitative recoveries ranged from 91.07% to 111.75%. The results suggested that combination of shotgun proteomics and MRM had potential for the milk species authentication.

Assessment of cheese frauds, and relevant detection methods: A systematic review

Dairy products are widely consumed in the world due to their nutritional and functional characteristics. This group of food products are consumed by all age groups due to their health-giving properties. One of these products is cheese which has a high price compared to other dairy products. Because of this, it can be prone to fraud all over the world. Fraud in food products threatens the world's food safety and can cause serious damage to human health. There are many concerns among food authorities in the world about the fraud of food products. FDA, WHO, and the European Commission provide different legislations and definitions for fraud. The purpose of this review is to identify the most susceptible cheese type for fraud and effective methods for evaluating fraud in all types of cheeses. For this, we examined the Web of Science, Scopus, PubMed, and ScienceDirect databases. Mozzarella cheese had the largest share among all cheeses in terms of adulteration due to its many uses. Also, the methods used to evaluate different types of cheese frauds were PCR, Spectrometry, stable isotope, image analysis, electrophoretic, ELISA, sensors, sensory analysis, near-infrared and NMR. The methods that were most used in detecting fraud were PCR and spectrometry methods. Also, the least used method was sensory evaluation.

Animal Species Authentication in Dairy Products

Milk is one of the most important nutritious foods, widely consumed worldwide, either in its natural form or via dairy products. Currently, several economic, health and ethical issues emphasize the need for a more frequent and rigorous quality control of dairy products and the importance of detecting adulterations in these products. For this reason, several conventional and advanced techniques have been proposed, aiming at detecting and quantifying eventual adulterations, preferentially in a rapid, cost-effective, easy to implement, sensitive and specific way. They have relied mostly on electrophoretic, chromatographic and immunoenzymatic techniques. More recently, mass spectrometry, spectroscopic methods (near infrared (NIR), mid infrared (MIR), nuclear magnetic resonance (NMR) and front face fluorescence coupled to chemometrics), DNA analysis (real-time PCR, high-resolution melting analysis, next generation sequencing and droplet digital PCR) and biosensors have been advanced as innovative tools for dairy product authentication. Milk substitution from high-valued species with lower-cost bovine milk is one of the most frequent adulteration practices. Therefore, this review intends to describe the most relevant developments regarding the current and advanced analytical methodologies applied to species authentication of milk and dairy products.

Authenticity assessment of dairy products by capillary electrophoresis

Milk and derivatives are a very important part in the diet of the world population. Products from goat, buffalo, and sheep species have a greater economic value than the cow ones, therefore, authenticity frauds by improperly adding cow's milk occur frequently: dairy products are among the seven more attractive foods for adulteration. Milk from each of the above-cited animal species has its own definite profile of whey proteins (variants of α-lactalbumin and β-lactoglobulin) and its definite profile of caseins (variants of α_S1 -, α_S2 -, β-, and κ-casein). Such proteins can be usefully exploited as markers of authenticity by using capillary electrophoresis which is the technique of choice for the analysis of proteins. Due to the multiple adjustable parameters that are unknown to other analytical techniques, capillary electrophoresis is able to detect frauds in milk mixtures and cheese with little use of solvents, fast analysis time, and ease of operation. This makes it attractive and competitive for routine checks that are very important to fight the adulteration market. Advantages and limitations are discussed.

Determination of volatile organic compounds in Slovak bryndza cheese by the electronic nose and the headspace solid-phase microextraction gas chromatography-mass spectrometry

The aim of the present study was to describe volatile organic compounds of the traditional Slovak bryndza cheese determined by using an electronic nose (e-nose) and a gas chromatography mass spectrometry (GCMS) with head-space solid phase microextraction (HS-SPME). For the first time, e-nose based on the gas chromatography principle with a flame ionization detector was described to identify and quantify aroma active compounds of bryndza cheese from Slovakia. The e-nose detects aroma compounds of very small concentrations in real-time of a few minutes and identifies them by comparing Kovats´ retention indices with the NIST library. Bryndza cheese produced from unpasteurized ewe´s milk and from a mixture of raw ewe´s and pasteurized cow´s types of milk were collected from 2 different Slovak farms beginning in May through to September 2019. The flavour and aroma of bryndza cheese are apparently composed of compounds contained in milk and the products of fermentation of the substrate by bacteria and fungi. Regarding volatile organic compounds, 25 compounds were detected and identified by an electronic nose with a discriminant >0.900 with ethyl acetate, isopentyl acetate, 2-butanone, acetic acid, butanoic acid, and butane-2,3-dione confirmed by gas chromatography. We confirm the suitability of the electronic nose to be used for monitoring of bryndza cheese quality.

Characteristics of textural and sensory properties of Oštiepok cheese

Oštiepok is a traditional half-fat semi-hard cheese made in Slovakia. The basic raw material used to produce oštiepok cheese is ewe's milk, a mixture of ewe's and cow's milk or cow's milk. Oštiepok cheese is produced either directly at a small-scale mountainside sheep farm, using the traditional on-farm method of production, or at dairies, using the industrial method. Oštiepok cheese was produced as far back as the beginning of the 18th century. An industrial production of Oštiepok cheese using cow's milk were laid by the Galbavý family in Detva (Slovakia) in 1921. The cheese is originally made by cutting off fresh sweet cheese, which is pressed into a wooden, hand-cut and decorated round shape where it is left to stand. Subsequently, it is removed and immersed in warm salty water, left to stand there until the salt penetrates completely in. Then it is necessary that it pass slightly. In its salty water, the ostrich produces its traditional durability, its surface is slightly peeled, mostly yellowish. This cheese may or may not be steamed and may be smoked or unsmoked. Slovenský oštiepok is a protected trade name under the EU's protected geographical indication. A similar cheese is made in the Polish Tatra Mountains under the name Oscypek. The cheeses differ in ingredients' ratios, cheesemaking process and the characteristics of the final products. In this study we have characterized textural and sensory properties of the Oštiepok cheese produced in Slovakia made from ewe's milk, a mixture of ewe's and cow's milk and cow's milk.

Authentication of caprine milk and cheese by commercial qPCR assay

The objective of the study was to investigate potential adulteration of commercial caprine milks and cheeses with bovine milk using commercial qPCR assay. The assay comprised of bovine-, ovine- and caprine-specific primers and TaqMan probe and mammalian internal control. Specificity, sensitivity, linearity, reproducibility and efficiency of the bovine assay were tested as well. Specificity was verified by running reaction on the DNA of other milk-producing species (caprine and ovine) and made-up bovine-caprine (v/v) milk mixes. In both experiments, a bovine DNA fragment was amplified whereas no amplification was obtained from the other species. Sensitivity, linearity, reproducibility and efficiency were tested on 10-fold dilution series of 10 ng bovine DNA. The assay has shown good linearity (R2 = 0.983) within whole range, with efficiency of 86% and excellent reproducibility (SD around the CT for the technical replicates <0.5). The sensitivity was adequate, as calculated LOD and LOQ were 1.44 pg and 2.94 pg of bovine DNA, respectively. Finally, the assay was used to authenticate 5 caprine milk samples and 5 caprine cheese samples, purchased from local supermarkets. Totally, 1 milk sample has shown the fluorescence signal, which exceeded baseline in cycle 39.01 ±0.69. However, the signal was above LOD and LOQ suggesting that there could not be unambiguously declared any adulteration with bovine milk. Amplification of bovine-specific DNA was not observed in the other samples indicating products were not adulterated. The commercial qPCR assay has proved that real-time PCR assays, as well as DNA-based techniques in a general, are the excellent and reliable tools for fighting with frauds in the food industry and protecting the public health. 

Detection of ovine milk adulteration using taqman real-time pcr assay

Food safety, quality and composition have become the subjects of increasing public concern. To prevent fraud and enhance quality assurance, credible analysis of dairy products is crucial. Bovine milk is more widely available and cheaper than milk of sheep and goat. Bovine milk is also processed in large quantities to produce a range of dairy produce. DNA-based methods have proven to be more reliable, because of the stability of DNA under the conditions of high temperature, high pressure, and chemical treatment used during the processing of some food products. The commercial InnuDETECT cheese assay based on the principle TaqMan real-time PCR systems have been tested for the identification and quantification of bovine DNA in ovine milk samples. DNA was extracted using the InnuPREP DNA Mini Kit and quantified by the QuantiFluor dsDNA system. The assay showed good linearity, with correlation coefficient of R2 = 0.983 and efficiency of 86%. The internal control amplified fragment from different mammalian species (cow, sheep and goat), with similar CT values. Detection of bovine DNA in milk mixtures was achieved even in samples containing 0.5% of bovine milk. The InnuDETECT cheese assay has been successfully used to measure bovine DNA in ovine milk, and will prove useful for bovine species identification and quantitative authentication of animal-derived products.